1. Field of the Invention
The present invention relates to a medical apparatus for non-traumatic grasping, manipulating and closure, and more particularly to an integrated steerable grasper and snare deploying medical apparatus for left atrial appendage isolation and closure. The invention is useful in access or approaches which do not require intercostals penetrations; however the present invention is not limited to any particular approach or access methodologies.
2. Background Information
Atrial fibrillation is a relatively common cardiac rhythm disorder affecting a population of approximately 2.5 million patients in the United States alone. Atrial fibrillation results from a number of different causes and is characterized by a rapid chaotic heart beat. During this type of fibrillation, the atria, rather than the sinus node, initiates the impulses which cause contraction of the heart muscle. In some patients, atrial fibrillation may occur in the absence of any other known disease. These impulses are relatively rapid and erratic, and are known to not properly control the contractions of the heart. As a result, the atria beat faster than the ventricles, the ventricular contractions are irregular, the ventricles do not completely fill, with blood, and the ventricular contractions eject less blood into the greater vessels.
The atrial appendages are especially important in the transport of blood because they have a sack-like geometry with a neck potentially more narrow than the pouch. In this case, contraction of the appendage is essential to maintain an average absolute blood velocity high enough to eliminate potential stasis regions which may lead to thrombus formation. One of the many problems caused by atrial fibrillation is the pooling of blood in the left atrial appendage during fibrillation. When blood pools in the atrial appendage, blood clots can accumulate therein, build upon themselves, and propagate out from the atrial appendage into the atrium. These blood clots can cause serious problems when the heart resumes proper operation (normal sinus rhythm) and the blood, along with the blood clot(s), is forced out of the left atrial appendage. Similar problems also occur when a blood clot extending from an atrial appendage into an atrium breaks off and enters the blood supply. More specifically, the blood from the left atrium and ventricle supply the heart and brain. Thus, the blood flow will move the clots into the arteries of the brain and heart which may cause an obstruction in blood flow resulting in a stroke or heart attack. Consequently, patients with atrial fibrillation also have an increased risk of stroke. It has been estimated that approximately 75,000 atrial fibrillation patients each year suffer a stroke related to that condition.
Significant efforts have been made to reduce the risk of stroke in patients suffering from atrial fibrillation. Most commonly, those patients are treated with blood thinning agents, such as warfarin, to reduce the risk of clot formation. While such treatment can significantly reduce the risk of stroke, it also increases the risk of bleeding and for that reason is inappropriate for many atrial fibrillation patients.
An alternative to the drug therapy is a procedure that closes (stitch off or remove) the left atrial appendage in patients which are prone to atrial fibrillation. Most commonly, the left atrial appendage has been closed or removed in open surgical procedures, typically where the heart has stopped and the chest opened through the sternum. Because of the significant risk and trauma of such procedures, left atrial appendage removal occurs almost exclusively when the patient's chest is opened for other procedures, such as coronary artery bypass or valve surgery.
For that reason, alternative procedures which do not require opening of the patient's chest, i.e., a large median sternotomy, have been proposed. U.S. Pat. No. 5,306,234 to Johnson describes a thoracoscopic procedure where access to the pericardial space over the heart is achieved using a pair of intercostal penetrations (i.e., penetrations between the patients ribs) to establish both visual and surgical access. While such procedures may be performed while the heart remains beating, they still require deflation of the patient's lung and that the patient be placed under full anesthesia. Furthermore, placement of a chest tube is typically required to re-inflate the lung, often requiring a hospitalization for a couple of days.
U.S. Pat. No. 5,865,791, to Whayne et al. describes a transvascular approach for closing the left atrial appendage. Access is gained via the venous system, typically through a femoral vein, a right internal jugular vein, or a subclavian vein, where a catheter is advanced in an antegrade direction to the right atrium. The intra-atrial septum is then penetrated, and the catheter passed into the left atrium. The catheter is then positioned in the vicinity of the left atrial appendage which is then fused closed, e.g., using radiofrequency energy, other electrical energy, thermal energy, surgical adhesives, or the like. Whayne et al. further describes a thoracoscopic procedure where the pericardium is penetrated through the rib cage and a lasso placed to tie off the neck of the left atrial appendage. Other fixation means described include sutures, staples, shape memory wires, biocompatible adhesives, tissue ablation, and the like. The transvascular approach suggested by Whayne et al. is advantageous in that it avoids the need to penetrate the patient's chest but suffers from the need to penetrate the intra-atrial septum, may not provide definitive closure, requires entry into the left atrial appendage which may dislodge clot and requires injury to the endocardial surface which may promote thrombus formation. A thoracoscopic approach which is also suggested by Whayne et al. suffers from the same problems as the thoracoscopic approach suggested by Johnson.
U.S. Pat. No. 6,488,689, to Kaplan et al. describes a sub-xiphoid approach for closing the left atrial appendage, and is incorporated herein by reference. The Kaplan patent discloses a tool 10 for such a closure that includes a grasper 30 and a second capture loop 32 operated by thumb guides 40 and 42 respectively. The grasper 30 and capture loop 32 extend though lumens 20, 22 or 24 in an extended body of the tool 10. The tool 10 of the Kaplan patent does not provide an efficient, convenient mechanism to actuate the grasper 30, to advance the capture loop 30, or to minimize the cutting effects of the capture loop 30. The Kaplan et al. patent further describes a clip applying surgical device that suffers from similar difficulties.
There is a need for a surgically acceptable tool for minimally invasive left atrial appendage closure. Such a tool would be capable of being used on patients who have received only a local anesthetic and whose hearts have not been stopped. It would be further desirable to provide an effective, efficient, easily utilized surgical tool that allows for procedures which approach the left atrial appendage without the need to perform a thoracotomy (i.e. penetration through the intercostal space) or the need to perform a transeptal penetration and/or perform the procedure within the left atrium or left atrial appendage. At least some of these objectives will be met by the inventions described herein below.
It is the objects of the present invention to address the deficiencies of the prior art discussed above and to do so in an efficient cost effective manner